1. Field of the Invention
The present invention relates to a pump, system and method for collecting and containing gaseous substances. More specifically, the present invention is directed to the collection and containment of unknown and potentially hazardous gases by a system including a pump which generates a suction using the flow of an essentially chemically inert fluid.
2. Description of the Prior Art
The present invention is particularly suited for application in the field of hazardous waste management, and more specifically to the recontainerization, disposal, and/or scrubbing of the contents of deteriorated compressed gas cylinders. U.S. Pat. No. 4,944,333 (hereinafter the "'333 patent") and U.S. Pat. No. 4,690,180 (hereinafter the "'180 patent") disclose a system for the safe rupturing of deteriorated compressed gas cylinders. Both the '180 and '333 patents are hereby incorporated by reference into this specification.
The unique environment for which the system of the present invention is particularly suited demands that the pump which drives the system function reliably regardless of the type of gas which is processed. Waste gas cylinders often bear no recognizable markings which identify the gas or gases contained in the cylinders. The gas may be entirely harmless such as air or nitrogen. On the other hand, the gas may be highly flammable, reactive, corrosive, toxic, or poisonous. A system to process unknown gases must be able to safely handle the wide variety of gases to which it may be exposed.
A difficulty with the prior art resides in the inability of vacuum pumps, which have been conventionally used in such systems, to resist degradation when exposed to corrosive gases. As a general rule, the most economically feasible and effective conventional vacuum pump used in the past has been the rotary vane vacuum pump.
Within the housing of the conventional rotary vane vacuum pump, the gas inlet port and gas outlet port are physically near one another. The rotary vane within the housing draws the gas through the gas inlet port, compresses it by reducing its physical volume, and exhausts the gas, now pressurized, through a gas outlet port. To maintain an adequate seal between the rotary vane and the housing, the conventional pump depends upon the maintenance of a film of oil between the rotary vane and the housing. If the oil film breaks down, the conventional pump can not draw a vacuum.
The oil film in the conventional pump is particularly sensitive to certain environmental conditions. Certain gases may interfere with the wetting action of the film. Other gases, such as corrosive gases, may react with the rotary vane and housing to pit and soar the metal surfaces. Once the moving elements of such a pump are scarred, the oil cannot form an adequate seal between the rotary vane and the housing. It is also possible that potentially flammable gases may ignite within the housing of the conventional pump and cause scarring of the moving parts. The oil seal of the conventional pump may be compromised by any of these conditions, each of which can prevent the pump from drawing a vacuum. When such a pump is then required to extract a poisonous or toxic gas from a compressed gas cylinder, the probability that the gas may leak and cause serious injury is increased.
Due to the sensitivity of conventional pumps to various gaseous environments, these pumps have been found to break down after only a few hours of operation, especially when the conventional pump is subjected to corrosive gases. When the pump becomes inoperable, the entire system becomes disabled. This problem not only makes it more expensive to collect and contain hazardous gases but presents various safety hazards.